MONTPELIER, Vt. — Stymied by snow, frozen ground and a vague lead, homicide investigators have postponed a search for the remains of an elderly woman with Alzheimer's disease who police say was shot to death and incinerated by her daughter and buried by her grandson.

"Unfortunately, Vermont in winter really doesn't help us out when we're trying to do this type of search," said Major Ed Ledo, commander of the Vermont State Police's criminal division. "You're putting people out there in below-zero weather with wind blowing, and you're trying to dig through frozen ground. Not very productive."

Investigators will resume searching in the spring for the remains of Mary Wilcox, a 78-year-old Westford woman who suffered from Alzheimer's disease and was reported missing by her family in 2006.

Prosecutors said last week that she was shot to death by her 59-year-old daughter, Jeanne Sevigny, who then burned the body in a backyard fire pit and put the charred remains in a suitcase that she gave to her son to bury.

She's charged with second-degree murder and is being held without bail. Police said she told them that Wilcox was shot during a struggle that began when Sevigny found her with a pistol and tried to take it away from her. Gregory Sevigny is charged with unlawful disposal of a body.

According to a police affidavit, Gregory Sevigny said the remains consisted of a skull, spinal cord and bones, which he said he buried next to a big rock on a trail behind the school.

Crime scene investigators spent three days searching for the remains in the woods behind the red brick elementary school and used cadaver-sniffing dogs, but were unable to find them.

"You want to move away the debris on the ground to see if it's been disturbed or possibly dug there, but with snow, frost and bitter cold, and not having a precise location of where she was disposed of, it's very difficult," Ledo said Wednesday.

He said Gregory Sevigny, through his attorney, was trying to assist but that the burial occurred at night and in foul weather, and it was three years ago. Asked if police believe Gregory Sevigny was being truthful in describing the location, Ledo said: "He's trying to remember as best as he can, but who's to say? We're taking him for his word on where he recalls disposing of the remains."

His lawyer, Bob Katims, said Sevigny was being as helpful as he could be to police.

Katims acknowledged that the absence of a body — and the fact that the pistol used hasn't been found — could be a problem for prosecutors.

"I don't know what the ramifications would be if nothing's ever found. It certain presents challenges to the prosecution, but there may be ways around those challenges. We'll just see what happens," Katims said.

The prosecutor in the case, Chittenden County State's Attorney T.J. Donovan, said he is confident in the evidence gathered to date but that the investigation will continue.